A standard drill chuck such as described in U.S. Pat. No. 5,765,839 has a chuck body rotatable about a chuck axis and provided centered on the axis with an annular array of teeth each having a steep flank and a shallow flank and a plurality of jaws angularly spaced on the body about the axis and radially displaceable relative to the body between inner and outer positions. A tightening ring is axially fixed but rotatable about the axis on the body in a tightening direction and in an opposite loosening direction and a pair of screwthread formations between the tightening ring and the jaws move the jaws radially together on rotation of the tightening ring in the tightening direction and radially apart on rotation of the tightening ring in the loosening direction. A locking member engageable with the teeth and angularly fixed on the tightening ring is radially displaceable between a locking position engaging the teeth and preventing rotation of the body relative to the tightening ring in the loosening direction and a freeing position permitting free rotation of the body relative to the tightening ring in both directions. A sleeve axially fixed but angularly displaceable on the tightening ring is formed with a pair of angularly spaced and radially open seats. A pair of angularly spaced abutments between the sleeve and the tightening ring limit angular movement of the sleeve on the tightening ring to movement between a pair of end positions of the sleeve on the tightening ring. A cam on the sleeve is engageable with the locking member for displacing the locking member into the locking position when the sleeve is in one of its end positions and for displacing the locking member into the freeing position when the sleeve is in the other of its end positions. A latch member angularly fixed on the tightening ring is engageable in the seats of the sleeve for releasably retaining the sleeve in its end positions. A common spring extending angularly along and fixed angularly in the tightening ring urges the latch member into the seats and the locking member into the freeing position.
With this system the sleeve serves both to position the locking member and to rotate the ring. When tightening the chuck, the sleeve merely rotates the tightening ring with the locking member ratcheting or sliding over the shallow backs of the sawteeth of the chuck body. When loosening, the sleeve at first rotates relative to the tightening ring to pull the locking member out of engagement with the teeth and subsequent backward rotation of the sleeve entrains the locking ring and opens the chuck. Thus the sleeve can in fact constitute the entire outside surface of the chuck, making it extremely simple to handle. The locking feature of the chuck is automatic, that is the chuck is automatically locked when tightened and automatically unlocked when loosened.
The advantage of this system is that rotation in the tightening direction tightens the jaws on the tool and, once they are solidly engaged with the tool, locks the chuck. Opposite rotation when the chuck is clamped on a tool first unlocks the chuck and then spreads the jaws to release the tool.
In order to hold the chuck body still during the tightening/locking rotation and the unlocking/loosening rotation, it is standard to provide a holding ring or the like fixed on the chuck body and exposed adjacent the tightening ring or sleeve so that the user can grip the holding ring with one hand and the tightening ring with the other to relatively rotate them. In other systems a spindle lock is provided on the drill which allows the chuck body to be arrested. In such arrangements the holding ring is, therefore, superfluous.